Hydrostatic cyclic expansion extrusion process for producing ultrafine-grained rods

ABSTRACT

A method of producing ultrafine-grained materials and a system for mass production of ultrafine-grained materials is disclosed. The system includes a die assembly with a die channel that extends from a first end to a second end. The system also includes first punch and a second punch. A lubricant is poured into a portion of the die channel to surround a workpiece that is positioned within the die channel in order to minimize the effects of friction during processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from Iran PatentApplication Serial Number 139550140003008482, filed on Oct. 5, 2016, andentitled “HYDROSTATIC CYCLIC EXPANSION EXTRUSION (HCEE) PROCESS FORPRODUCING UFG HIGH STRENGTH LONG RODS,” which is incorporated herein byreference in its entirety.

BACKGROUND

Ultrafine-grained and nanostructured materials are materials thatpossess particularly high strength. Structures made of ultrafine-grainedand nanostructured materials are often suitable for making lighter andat the same time energy efficient vehicles, airplanes, and othermachinery. A variety of methods have been developed to produceultrafine-grained (UFG) materials. For example, processing through theuse of various metalworking techniques such as severe plasticdeformation (SPD) can apply strain to produce ultrafine grained andnanostructured materials. In some cases, SPD may be understood as aprocess in which high strain is applied without any significant changein the dimensions of a workpiece.

SUMMARY

This summary is intended to provide an overview of the subject matter ofthis patent, and is not intended to identify essential elements or keyelements of the subject matter, nor is it intended to be used todetermine the scope of the claimed implementations. The proper scope ofthis patent may be ascertained from the claims set forth below in viewof the detailed description below and the drawings.

In one aspect, the present disclosure is directed to a method ofproducing ultrafine grain materials that includes positioning aworkpiece in a die channel, the die channel being formed in a dieassembly, pouring lubricant into a first end of the die channel, therebysubstantially surrounding the workpiece with the lubricant, and moving afirst punch toward the workpiece and thereby pushing the workpiecetoward a second end of the die channel.

The above general aspect may include one or more of the followingfeatures. For example, the method can further include inserting a firstseal into the first end of the die channel, thereby sealing thelubricant in the die channel. The method can also include a step ofinserting the first punch into the first end of the die channel, as wellas inserting a second punch into the second end of the die channel. Insome cases, the method can include rotating the die assemblyapproximately 180 degrees to complete a first pass, and/or pouringadditional lubricant into the second end of the die channel during asecond pass. In addition, in some implementations, the method includesinserting a second seal into the second end of the die channel duringthe second pass, and/or inserting the first punch into the second end ofthe die channel. In another example, the method can include removing thesecond punch from the die assembly, and/or removing the first seal fromthe die assembly.

In another aspect, the present disclosure is directed to a die assemblyfor production of ultrafine-grain materials that includes a first diesegment including a first die portion joined to a first panel portionand a second die segment including second die portion joined to a secondpanel portion. In addition, the first die segment is removably attachedto the second die segment.

The above general aspect may include one or more of the followingfeatures. For example, the die assembly can further include a firstplurality of fasteners configured to attach the first die portion to thefirst panel portion. In another example, the first panel portion mayinclude a gasket. In some implementations, the first die portion has asubstantially cylindrical shape, and/or the second die portion has asubstantially cylindrical shape. In one implementation, the first dieportion and the first panel portion include a plurality of apertures forreceiving the first plurality of fasteners. In addition, in some cases,the die assembly includes a set of connectors configured to removablyattach the first die segment to the second die segment. In one example,a die channel extends from the first die segment to the second diesegment. In some implementations, the die channel includes an expansionsection and an extrusion section, and a lubricant may fill or bedisposed within the die channel, the lubricant being configured tosubstantially surround an entire exterior surface of a workpiecedisposed in the die channel. Furthermore, the die assembly can beconfigured to apply hydrostatic pressure to a workpiece. In oneimplementation, a second plurality of fasteners may be configured toattach the second die portion to the second panel portion.

Other systems, methods, features and advantages of the implementationswill be, or will become, apparent to one of ordinary skill in the artupon examination of the following figures and detailed description. Itis intended that all such additional systems, methods, features andadvantages be included within this description and this summary, bewithin the scope of the implementations, and be protected by thefollowing claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The implementations can be better understood with reference to thefollowing drawings and description. The components in the figures arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of the implementations. Moreover, in thefigures, like reference numerals designate corresponding partsthroughout the different views.

FIGS. 1A and 1B depict an implementation of an overview and progressionof a hydrostatic cyclic expansion extrusion system;

FIG. 2 depicts an implementation of a method of hydrostatic cyclicexpansion extrusion;

FIG. 3 is an exploded view of an implementation of a die assembly.

FIG. 4 is an cross-sectional view of an implementation of the dieassembly of FIG. 3;

FIG. 5A is a photograph of an implementation of a product formed by ahydrostatic cyclic expansion extrusion process assembly; and FIG. 5Bshows evolution grain size from unprocessed to HCEE processed after twopasses;

FIGS. 6 graphs presenting a hardness distribution in an annealed sampleand the hydrostatic cyclic expansion extrusion process; and

FIG. 7 is a graph presenting stress-strain data of unprocessed and HCEEprocessed samples.

DETAILED DESCRIPTION

In the following detailed description, various examples are presented toprovide a thorough understanding of inventive concepts, and variousaspects thereof that are set forth by this disclosure. However, uponreading the present disclosure, it may become apparent to persons ofskill that various inventive concepts and aspects thereof may bepracticed without one or more details shown in the examples. In otherinstances, well known procedures, operations and materials have beendescribed at a relatively high-level, without detail, to avoidunnecessarily obscuring description of inventive concepts and aspectsthereof.

As compared to more conventional coarse grained materials, UFG materialstypically demonstrate highly improved mechanical, chemical and physicalproperties. In conventional Cyclic Expansion Extrusion (CEE) processes,long metal articles cannot be formed, because increased friction forcescause a fracture of the die and failure in the die. In the followingdisclosure, a Hydrostatic Cyclic Expansion Extrusion (HCEE) process isintroduced, a process in which the limiting effects of friction isremoved and workpieces of greater quality may be produced. In the HCEEprocess, the workpiece does not come into contact with the die and metalforming is achieved through pressurized lubricating fluid. Inconventional methods, friction remains a limiting factor, making theproduction of long metal articles difficult or impossible.

Thus, an objective of the present disclosure is to present a novelprocess that allows for the production of workpieces without limitationon the length of the workpiece. For purposes of reference, this processwill be referred to as Hydrostatic Cyclic Expansion Extrusion (HCEE).Generally, in HCEE, deformation is achieved through the application ofcompressed fluid, thereby reducing or eliminating friction. Thisreduction in friction can allow the HCEE process to be substantiallyindependent of the length of the workpiece, making it possible tofabricate ultrafine grained materials of longer lengths. Thus the HCEEprocess makes the mass production of long metal UFG articles possible.

Referring to FIG. 1A, a schematic view of an implementation of an HCEEsystem 210 is depicted. In different implementations, HCEE system 210can include a die assembly 150, an upper punch assembly (“upper punch”)110, a lower punch assembly (“lower punch”) 160, and a lubricating fluid(“lubricant”) 130. A workpiece 140 is shown in the system for purposesof clarity. In some implementations, a sealant or seal 120 may also beused in HCEE system 210.

In different implementations, a cyclic extrusion expansion (CEE) systema die can comprise an axisymmetric barrel-like hollow, as well as one ormore punches that can control or impose a flow of material. An extrusionsection is placed after the part in which the sample experiencesexpansion. In one implementation, the force needed to extrude thematerial also provides the appropriate amount of back-pressure forexpansion. Within the die cavity, the cylindrical material is initiallyexpanded in diameter and then shrunk (usually returned to its originaldiameter) through an extrusion configuration. The material undertakestwo portions of straining at expansion and extrusion. It can beunderstood that the HCEE process described herein can incorporate someor all features of the CEE system.

Referring now to FIG. 1A, in the HCEE apparatus, it can be seen thatlubricant 130 fills a space between die assembly 150 and workpiece 140.In some implementations, lubricant 130 can be pressurized. In oneimplementation, a pressurized lubricating fluid covers the entireexterior of the workpiece, thereby minimizing friction. By substantiallyor entirely surrounding the workpiece with a lubricant, as shown in FIG.1A, the process remains independent of the length of the workpiece asthe effect of friction is reduced or eliminated. Thus, workpieces ofvirtually any length can be fabricated. As an example, a magnified viewof a portion of workpiece 140 is provided, which identifies an expandedportion with a first diameter 180 and an extruded portion with a seconddiameter 190, where second diameter 190 is smaller than first diameter180. In other words, the region in which the diameter begins to expandtoward a center of the die channel provides an expansion section 102,and a second section from the center of the die channel toward anarrowing region of the die channel provides an extrusion section 104.In addition, as generally represented by an angle 170, it can be seenthat the curvature of the workpiece changes as it passes through theexpansion section of the die assembly.

Referring now to both FIGS. 1A and 1B, an implementation of a method ofutilizing the HCEE system is described. In FIG. 1B, a schematic view ofthe method is depicted. As shown in FIG. 1B, in a first stage 210, theprimary punch or upper punch 110 descends and/or moves in a directiontoward workpiece 140 that is placed in the apparatus. Initially, theexit (e.g., the lower end of the “barrel” or channel) can be blocked bya second punch or lower punch 160. Lower punch 160 can act as a backingplate in one implementation. This arrangement can allow pressureassociated with the primary punch cause a radial flow of the materialuntil the material is pressed against the inner walls of the channel. Inother words, the material may expand and take on the shape of thechannel, as shown in a second stage 220. As depicted in both first stage210 and second stage 220, lubricant 130 substantially surroundsworkpiece 140 throughout the process, reducing or eliminating frictionbetween the workpiece and the inner surface of the channel and improvingthe efficient passage of the material through the system. In someimplementations, the workpiece can expand against the pressurizedlubricating fluid that surrounds the workpiece during first stage 210and/or second stage 220.

In a third stage 230, lower punch 160 that had blocked the exit(associated with a second end 280 disposed toward the lower end of thedie assembly) is removed, whereby the necessary back-pressure forexpansion of the workpiece is provided by the subsequent extrusion thatoccurs after the expansion. Upper punch 160 moves further inward ordownward through a first end 270, pushing the material such that itflows through the die cavity or die channel, and moving the workpiecematerial downward to its end point. At this point, the workpiece hasgone through one pass of the HCEE process. If desired, additional passescan be performed, as represented by a fourth stage 240, where theapparatus (including workpiece 140) can be rotated approximately 180degrees, such that first end 270 is now disposed toward the lower end ofthe die assembly and second end 280 is now disposed toward the upper endof the die assembly. After the assembly has been rotated, additionallubricant 230 is poured into the die, and another seal 220 can be addedtherein. The upper punch 160 can then be inserted or entered through theopposite opening (what had been the end associated with the exit),pressing the workpiece in a direction opposite to the previousdirection. The additional lubricant ensures that friction continues tobe minimized during the procedure. The apparatus can be rotated and theprocess can be performed any number of times until the workpiece is inthe desired condition. In some cases it is necessary to remove theprevious seal before refilling or pouring additional lubricant into thecavity.

In FIG. 2, a flow chart is presented in which an implementation of anHCEE method is provided. As shown in FIG. 2, a first step 201 caninvolve positioning a workpiece in a die channel, where the die channelis formed in a die assembly. In a second step 202, lubricant is pouredinto the die channel via the first or upper end, such that the lubricantsubstantially surrounds the workpiece. The first punch assembly can beinserted into the first end of the die channel. A lower or second punchassembly or backplate can also be positioned within the lower end of thedie channel (a second end that is disposed opposite to the first endthat served as an entryway for the lubricant). In an optional third step203, a seal is inserted above the lubricant via the first end of the diechannel, sealing the lubricant inside of the die channel. In a fourthstep 204, an upper or first punch assembly descends toward theworkpiece, pushing down against both the workpiece and the lubricantfluid, and causing the workpiece to move in a direction associated withthe second end of the die channel. In some implementations, the upperpunch assembly presses against the seal, which in turn exerts pressureon the lubricant fluid and the workpiece below. In a fifth step 205, thelower punch is removed after the deformation of the workpiece by (forexample) the chamber die, and the upper punch pushes further downward,moving the workpiece toward an endpoint associated with the lower orsecond end of the die assembly. In an optional sixth step 206, theapparatus can be rotated 180 degrees, and additional lubricant as wellas a second seal can be inserted into the die channel via the second end(now associated with an upper end of the die assembly), allowing theprocess to be repeated if desired in another pass. Thus, the first punchis inserted into the second end of the die channel during the secondpass, while the second punch is inserted into the first end of the diechannel during the second pass. It should be understood that in someimplementations, the first seal or the second seal can be removed asneeded to allow for the addition of lubricant during each pass, and thenreplaced to form a seal again.

In order to provide greater detail to the reader, an exploded view of animplementation of a die assembly for use in the HCEE system is presentednext in FIG. 3. In different implementations, die assembly 150 cancomprise a plurality of components that are attached, connected orjoined together. A first component comprising a first die portion 410 isconfigured to be attached to a second component comprising a first panelportion 420. In addition, a third component comprising a second dieportion 430 is configured to be attached to a fourth componentcomprising a second panel portion 440. First die portion 410 and seconddie portion 430 can comprise a substantially cylindricalthree-dimensional shape in some implementations. In one implementationfirst die portion 410 and/or second die portion 430 include asubstantially round or circular cross-sectional shape. In addition,first panel portion 420 and/or second panel portion 440 can comprisegenerally flat or relatively thin segments with a cross-sectional shapeand size similar to the cross-sectional shape and size of first dieportion 410 and/or second die portion 430. In some implementations,first panel portion 420 and/or second panel portion 440 comprisegaskets.

In different implementations, one or both set of components (i.e., firstdie portion 410 with first panel portion 420, and second die portion 430with second panel portion 440) are securely fitted together as shown inFIG. 3 by a plurality of fasteners 460 (for example, screws, threadedfasteners, or other connectors etc.) that are inserted into openings orapertures formed in each component. In one implementation, fourfasteners are used to join together each of the two sets of components,and each of the first die portion 410, second die portion 430, firstpanel portion 420, and second panel portion 440 include a plurality ofapertures that are aligned with the apertures of a neighboringcomponent, and the apertures are configured to receive fasteners. Thus,it can be understood that in one implementation, a first plurality offasteners are configured to attach or join together first die portion410 with first panel portion 420 and a second plurality of fasteners areconfigured to attach or join together second die portion 430 with secondpanel portion 440.

In addition, the four components are aligned and connected as shown inFIG. 3 by insertion of a plurality of elongated connectors 450. In someimplementations, there are two to eight elongated connectors. In FIG. 3,there are four elongated connectors, which are configured to extendthrough regions of first die portion 410, first panel portion 420,second die portion 430, and second panel portion 440 and securely jointhe assembly together. A substantially continuous and hollow cavity ordie channel is formed as the four components are linked together,extending through the first die segment and the second die segment. Indifferent implementations, the die assembly is designed as comprisingtwo main segments (i.e., first segment 470 and second segment 480) thatcan be readily separated and re-connected, facilitating the removal ofthe workpiece upon completion of the process. In other words, portionsof the die assembly may be removably attached to one another. Forpurposes of this disclosure, the term “removably attached” or “removablyinserted” shall refer to the joining of two components or a componentand an element in a manner such that the two components are securedtogether, but may be readily detached from one another. Examples ofremovable attachment mechanisms may include hook and loop fasteners,friction fit connections, interference fit connections, threadedconnectors, cam-locking connectors, compression of one material withanother, and other such readily detachable connectors.

For purposes of clarity, a cross-sectional view of die assembly 150 isalso provided in FIG. 4. As noted above, it can be seen that asubstantially continuous and hollow cavity or die channel 510 is formedas the four components are linked together. It can be understood that,in one implementation, the material of the workpiece is expanded in themiddle segment, and then it is extruded to regain its initial diameter.As a result of this severe deformation, as well as the strain imposed onthe workpiece, the microstructure of the workpiece changes and anultrafine-grained and/or nanostructured material can formed. Theapplication of hydrostatic pressure allows long UFG materials to befabricated, and improves the properties of the finished product.

For purposes of illustration, FIG. 5A includes a photograph of animplementation of a product formed by a hydrostatic cyclic expansionextrusion process. In one study, an aluminum alloy 1050 was used. Afterbeing processed in the HCEE apparatus, the aluminum alloy workpiece wasultrafine-grained. In addition, FIG. 5B depicts an OM micrograph of anannealed aluminum AL 1050 microstructure and TEM micrograph of the twocycles hydrostatic cyclic expansion extrusion processed sample.

Referring to FIG. 6, a graph presenting a hardness distribution in anannealed sample and first pass of an implementation of the hydrostaticcyclic expansion extrusion process is provided.

In addition, FIG. 7 is a graph presenting stress-strain data ofunprocessed and HCEE processed samples. In this case an annealedmicrostructured aluminium workpiece formed through a HCEE process wastested. It can be seen that the final strength of the product increasedby approximately 220 percent in the first pass of the HCEE process. Asthe number of passes the workpiece is exposed to increases, the strengthof the workpiece increases as well, as reflected by the curve associatedwith the second pass.

Thus, as presented herein, the HCEE process can provide for thefabrication of ultrafine-grained and/or nanostructured bulk articles inlong lengths. Testing of the process has shown that articles comprisingmaterials that have low formability in room temperature such asmagnesium can be produced. Furthermore, it should be understood that inaddition to the production of UFG long length rods at ambienttemperature, the disclosed HCEE process and apparatus can be used athigh temperature for materials that are not prone to deformation at room(or ambient) temperatures, such as magnesium and titanium, and othermaterials that deform only at relatively higher temperatures.

The inclusion of a layer of lubricating fluid provides the system withsubstantially reduced friction of the die as a result of the separationof the workpiece and the inner surface of the cavity. The production oflong materials with a favorable strength-weight ratio offer manyadvantages to the automotive and aerospace industry. With theelimination of the effects of friction in the disclosed HCEE process,the mass production of long metal articles of ultrafine grained andnanostructured materials become possible.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

Unless otherwise stated, all measurements, values, ratings, positions,magnitudes, sizes, and other specifications that are set forth in thisspecification, including in the claims that follow, are approximate, notexact. They are intended to have a reasonable range that is consistentwith the functions to which they relate and with what is customary inthe art to which they pertain.

The scope of protection is limited solely by the claims that now follow.That scope is intended and should be interpreted to be as broad as isconsistent with the ordinary meaning of the language that is used in theclaims when interpreted in light of this specification and theprosecution history that follows and to encompass all structural andfunctional equivalents. Notwithstanding, none of the claims are intendedto embrace subject matter that fails to satisfy the requirement ofSections 101, 102, or 103 of the Patent Act, nor should they beinterpreted in such a way. Any unintended embracement of such subjectmatter is hereby disclaimed.

Except as stated immediately above, nothing that has been stated orillustrated is intended or should be interpreted to cause a dedicationof any component, step, feature, object, benefit, advantage, orequivalent to the public, regardless of whether it is or is not recitedin the claims.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”or any other variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises a list of elements does not include only those elements butmay include other elements not expressly listed or inherent to suchprocess, method, article, or apparatus. An element proceeded by “a” or“an” does not, without further constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises the element.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various implementations. This is for purposes ofstreamlining the disclosure, and is not to be interpreted as reflectingan intention that the claimed implementations require more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed implementation. Thus, the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

While various implementations have been described, the description isintended to be exemplary, rather than limiting and it will be apparentto those of ordinary skill in the art that many more implementations andimplementations are possible that are within the scope of theimplementations. Although many possible combinations of features areshown in the accompanying figures and discussed in this detaileddescription, many other combinations of the disclosed features arepossible. Any feature of any implementation may be used in combinationwith or substituted for any other feature or element in any otherimplementation unless specifically restricted. Therefore, it will beunderstood that any of the features shown and/or discussed in thepresent disclosure may be implemented together in any suitablecombination. Accordingly, the implementations are not to be restrictedexcept in light of the attached claims and their equivalents. Also,various modifications and changes may be made within the scope of theattached claims.

1. A method of producing ultrafine grain materials comprising:positioning a workpiece in a die channel, the die channel being formedin a die assembly; pouring lubricant into a first end of the diechannel, thereby substantially surrounding the workpiece with thelubricant; and moving a first punch toward the workpiece and therebypushing the workpiece toward a second end of the die channel.
 2. Themethod according to claim 1, further comprising inserting a first sealinto the first end of the die channel, thereby sealing the lubricant inthe die channel.
 3. The method according to claim 1, further comprisinginserting the first punch into the first end of the die channel.
 4. Themethod according to claim 3, further comprising inserting a second punchinto the second end of the die channel.
 5. The method according to claim2, further comprising rotating the die assembly approximately 180degrees to complete a first pass.
 6. The method according to claim 5,further comprising pouring additional lubricant into the second end ofthe die channel during a second pass.
 7. The method according to claim6, further comprising inserting a second seal into the second end of thedie channel during the second pass.
 8. The method according to claim 7,further comprising inserting the first punch into the second end of thedie channel.
 9. The method according to claim 4, further comprisingremoving the second punch from the die assembly.
 10. The methodaccording to claim 7, further comprising removing the first seal fromthe die assembly.
 11. A die assembly for production of ultrafine-grainmaterials comprising: a first die segment including a first die portionjoined to a first panel portion; a second die segment including seconddie portion joined to a second panel portion; and the first die segmentbeing removably attached to the second die segment.
 12. The die assemblyof claim 11, further comprising a first plurality of fastenersconfigured to attach the first die portion to the first panel portion.13. The die assembly of claim 11, wherein the first panel portioncomprises a gasket.
 14. The die assembly of claim 11, wherein the firstdie portion has a substantially cylindrical shape.
 15. The die assemblyof claim 14, wherein the second die portion has a substantiallycylindrical shape.
 16. The die assembly of claim 11, wherein the firstdie portion and the first panel portion include a plurality of aperturesfor receiving the first plurality of fasteners.
 17. The die assembly ofclaim 11, further comprising a set of connectors configured to removablyattach the first die segment to the second die segment.
 18. The dieassembly of claim 11, further comprising a die channel extending fromthe first die segment to the second die segment.
 19. The die assembly ofclaim 18, wherein the die channel includes an expansion section and anextrusion section.
 20. The die assembly of claim 12, further comprisinga second plurality of fasteners configured to attach the second dieportion to the second panel portion.
 21. (canceled)
 22. (canceled)